yhsm-import-keys: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/sbin/yhsm-import-keys - from package: yhsm-yubikey-ksm

You may install the required package with command apt-get install {package}
Error in other languages:
yhsm-import-keys: bevel nie gevind nie
yhsm-import-keys: comandă negăsită
yhsm-import-keys: comando não encontrado
yhsm-import-keys: commande introuvable
yhsm-import-keys: command not found
yhsm-import-keys: käsku ei ole
yhsm-import-keys: không tìm thấy lệnh
yhsm-import-keys: komanda nerasta
yhsm-import-keys: Kommando nicht gefunden.
yhsm-import-keys: kommandot finns inte
yhsm-import-keys: komut yok
yhsm-import-keys: nie znaleziono polecenia
yhsm-import-keys: níor aimsíodh an t-ordú
yhsm-import-keys: no se encontró la orden
yhsm-import-keys: no s'ha trobat l'ordre
yhsm-import-keys: opdracht niet gevonden
yhsm-import-keys: parancs nem található
yhsm-import-keys: perintah tidak ditemukan
yhsm-import-keys: príkaz nenájdený
yhsm-import-keys: příkaz nenalezen
yhsm-import-keys: команда не найдена
yhsm-import-keys: командата не е открита
yhsm-import-keys: 命令找不到
yhsm-import-keys: コマンドが見つかりません